1. Field of the Invention
The present invention relates to a valve and a fuel cell using the same, and more particularly, relates to an ON-OFF valve having a pressure regulation mechanism and a fuel cell using the same.
2. Description of the Related Art
In recent years, environmental destruction has become a serious problem, and hence clean energy producing no harmful waste has been pursued. In addition, the depletion of fossil fuel has also become a problem, and new energy has been actively pursued. In electronic fields, concomitant with an increase of information, information processing capability has been significantly improved, and as a result, power consumption of electronic devices tends to increase.
Accordingly, as an energy source, attention has been paid to hydrogen which is contained in water exhaustlessly present on the globe, which has high chemical energy, and which produces no harmful waste. In particular, in a fuel cell which directly generates electrical energy, since hydrogen is efficiently used, and a large amount of electricity is generated, the fuel cell has been progressively applied to various fields, for example, including automobiles and portable electronic devices, such as a notebook personal computer, a mobile phone, and a video camera.
The fuel cell described above which generates electrical energy using hydrogen has a hydrogen electrode to which hydrogen is supplied and an oxidation electrode to which oxygen is supplied. In this fuel cell, hydrogen molecules are each separated into an electron and a proton by catalytic reaction on the hydrogen electrode, and the protons thus generated are allowed to pass through an electrolyte membrane and reach the oxidation electrode so as to form water by catalytic reaction with oxide molecules, thereby generating the flow of electrons, that is, electricity, in the process described above.
Unlike related cells, in fuel cells, charging is not required, and when a fuel is run out, electricity can be immediately generated only by refilling a fuel and can be advantageously used for operating a device for a long time.
Among the fuel cells described above, when attention is particularly paid to a small fuel cell used in a portable electrical device, since the amount of energy per volume and per weight generated by this type of fuel cell is several to approximately ten times that of a related fuel cell such as a lithium secondary fuel cell, an electrical device can be continuously operated for a longer time. Hence, in the field of the small fuel cell, research and development on the practical use thereof has been aggressively carried out.
As the small fuel cell described above, a direct methanol fuel cell (DMFC) using methanol as a fuel and a proton-exchange membrane fuel cell (PEFC) directly using hydrogen as a fuel have been developed and experimentally manufactured. In the former DMFC, problems, such as a crossover phenomenon in which methanol used as a fuel passes through a polymer electrolyte membrane and directly reacts with oxygen at an oxidation electrode side, and a poisoning phenomenon in which carbon monoxide generated through reaction poisons an electrode catalysis, may arise, and as a result, a fuel cell having a small output density can only be formed as compared to that obtained by the PEFC. On the other hand, advantageously, the latter PEFC can generate a larger amount of electricity and can only produce water without any byproducts; however, since hydrogen in the gas form is used, when the PEFC is used as a small fuel cell for a portable device, a handling technique of the cell becomes important.
In the PEFC using hydrogen as a direct fuel, as means for storing hydrogen, a hydrogen absorbing alloy having a large absorption capacity on a volume basis has been suitably used. However, when LaNi5 is used as a hydrogen absorbing alloy by way of example, since the pressure inside a hydrogen storage container becomes approximately 0.3 to 0.4 MPa at around room temperature, in order to prevent breakage of an electrolyte membrane which is caused by the difference in pressure, the pressure described above must be decreased to that at the oxidation electrode side, that is, approximately atmospheric pressure, when hydrogen is supplied into the fuel cell. In addition, for example, in the case in which the small fuel cell is not used for a long period of time, the output thereof may be decreased in some cases due to air entering the hydrogen electrode side, and hence a mechanism for purging the hydrogen electrode side with a pure hydrogen gas must be provided.
Furthermore, in addition to the fuel cell described above, in a system for regulating the flow of a fluid (including a liquid besides a gas), in general, a pressure regulation mechanism and an ON-OFF valve, such as an electromagnetic valve, functioning to open and close a flow path must be provided therein in some cases. In this case, since an element of regulating the pressure and an element of opening and closing the valve must be provided independently, a compact flow path cannot be freely designed due to the limitation described above.
Of course, miniaturization of a valve is very important for the small fuel cell described above, and in addition, for example, when a flow path is formed in a minute space as is the case of a microreactor which is believed to contribute the development of industries, the miniaturization described above is essentially required. When the valve is miniaturized, it is particularly important to form a compact flow path in a predetermined space.
A technique of solving the problem described above has been disclosed in Japanese Patent Laid-Open No. 05-141565, and in FIG. 13, reference numerals 102, 103, 104, 105, 106, 107, 108, 109, 110, and 111 indicate a stator, bobbin, coil, connector, terminal, auxiliary magnetic pole, body, fluid flow path, sheet portion, and step portion, respectively; reference numerals 114, 115, and 116 indicate a retainer, opening, and valve body, respectively; and reference numeral 118 indicates a check valve. As shown in FIG. 13, an electromagnetic valve has been disclosed in which, by using a spring 113 having a strong urging force for controlling a plunger 112 and a spring 117 having a weak urging force so that a check valve can be operated only by the difference in pressure between the upstream and the downstream sides of the check valve, the pressure regulation and the ON-OFF operation of the check valve can both be performed and in which the difference in pressure can be regulated by opening the check valve in accordance with the difference in pressure in the flow path when electricity is not supplied.
In addition, as a microvalve, ON-OFF valves have been disclosed, for example, in Japanese Patent Laid-Open Nos. 01-213523 and 2001-304440 and U.S. Pat. No. 5,325,880.
However, in the related technique disclosed in Japanese Patent Laid-Open No. 05-141565, since the spring is used as an elastic body, and an actuator is provided in the valve, the structure thereof becomes complicated and is difficult to be miniaturized. In addition, according to the structure described above, since the spring 117 is directly brought into contact with a fluid, when a corrosive fluid is used, the spring 117 may be degraded in some cases.
In addition, according to Japanese Patent Laid-Open Nos. 01-2135235 and 2001-304440 and U.S. Pat. No. 5,325,880, as the microvalve, the ON-OFF valve has been disclosed; however, the pressure regulation mechanism has not be disclosed. When the ON-OFF valve and the pressure regulation mechanism are both disposed in the flow path independently, the size of the whole flow path is increased, and as a result, the miniaturization thereof has a limitation.